This invention is based on and claims priority to Japanese Patent Application No. Hei 11-310,797, filed Nov. 1, 1999, the entire contents of which is hereby expressly incorporated by reference.
1. Field of the Invention
The present invention generally relates to fuel injection systems for internal combustion engines. More specifically, the present invention relates to control systems for fuel injection systems of such engines.
2. Related Art
In all fields of engine design, there is an increasing emphasis on obtaining more effective emission control, better fuel economy and, at the same time, increasing power output. This trend has resulted in the substitution of fuel injection systems for carburetors as the preferred air-fuel charge former.
Fuel injection systems typically inject fuel into air intake passage(s) or directly into combustion chamber(s) under the control of an electrically operated control unit. The control unit controls a volume of injected fuel. Typically, an engine speed sensor and a throttle valve position sensor are provided and respective signals from these sensors are used for determining suitable fuel volumes depending upon the sensed running condition of the engine. The fuel volumes are defined in a control map stored in the control unit. The control map can define the fuel volumes as corresponding to both the engine speed and the throttle valve position.
The signal from the throttle valve position sensor represents a volume of air introduced into the combustion chamber. The air amount, however, varies due to change of the atmospheric air pressure and other ambient conditions. In addition, the sensed level of air flow can be inaccurate due to flexing of a shaft on which the throttle valves are mounted. For instance, when the engine is being started, the engine may suddenly draw a large amount of air through the induction system and across the throttle valves. This sudden increase in air flow places a radial load on the throttle shaft. The radial load can cause the throttle valve shaft to flex and more air can pass beyond the throttle valves than the throttle valve sensor would indicate. Accordingly, the fuel injection amount may be inaccurate.
A need therefore exists for a fuel injection control system that would vary the amount of fuel injected during initial starting of the engine. In addition, to provide a more responsive fuel supply system, the amount of fuel injected can vary with engine speed and throttle position with a correction amount of fuel that depending on a rate of throttle position change.
Accordingly, one aspect of the present invention involves an engine for marine applications. The engine comprises at least one cylinder with a piston disposed within said cylinder. A cylinder head encloses a first end of said cylinder. A combustion chamber is at least partially defined by said cylinder, said piston and said cylinder head. An intake passage communicates with said cylinder head. A throttle valve is disposed along said intake passage. A throttle valve position sensor is adapted to detect a position of said throttle valve. A fuel injector is positioned downstream of said throttle valve. A fuel control system is capable of increasing a supplied amount of fuel in proportion to a rate of change of said position of said throttle valve and does not increase said supplied amount of fuel for a preset period following engine start.
Another aspect of the present invention involves a method of controlling a fuel injected engine. The method comprises engaging a starter motor, presetting a first fuel injection amount, decreasing said first fuel injection amount over a preset period of time, sensing a throttle position and controlling said fuel injection amount based at least in part upon said sensed throttle position after said preset period of time has elapsed.
A further aspect of the present invention involves an engine for marine applications. The engine comprises at least one cylinder with a piston disposed within said cylinder. A cylinder head encloses a first end of said cylinder. A combustion chamber is at least partially defined by said cylinder, said piston and said cylinder head. An intake passage communicates with said cylinder head. A throttle valve is disposed along said intake passage. A throttle valve position sensor is adapted to detect a position of said throttle valve. A fuel injector is positioned downstream of said throttle valve. Means are provided for increasing an amount of fuel injected based at least partially upon a rate of throttle valve movement only after a preset period of time has elapsed.